The present invention relates to a vehicle electronic controller, and more particularly, to a technique for checking for abnormality of a control microcomputer, which controls an actuator installed in a vehicle.
Electronic throttles are installed in some recent vehicles to electrically measure the amount an accelerating has been depressed and control the degree of opening of a throttle valve in accordance with the depressed amount of the pedal. A vehicle employing the electronic throttle includes an actuator for driving a throttle valve. Therefore, when the vehicle is provided with a constant velocity driving function, by adding a few input devices and making system software changes, the constant velocity driving function is achieved without adding a throttle valve drive actuator exclusively for constant velocity driving.
Japanese Laid-Open Patent Publication No. 6-307274 proposes separating the microcomputer, which controls the throttle valve opening degree, into a main microcomputer and a sub-microcomputer for safety when adding the constant velocity driving function to the electronic throttle. In a vehicle electronic controller described in the publication, the sub-microcomputer, which has the same functions as the main microcomputer, retrieves calculation results from the main microcomputer (e.g., throttle valve opening degree) and compares the results with results that are calculated by the sub-microcomputer. If the compared results do not match, the sub-microcomputer determines that the main microcomputer is not functioning normally and stops electronic control of the throttle.
However, in the vehicle electronic controller of the publication, the sub-microcomputer uses a determination value that is stored in a ROM of the sub microcomputer to check control data of the main microcomputer. Since the determination value differs between vehicles, a different sub microcomputer must be produced for each vehicle. This increases costs of the vehicle electronic controller.